Apparatuses for removal of hardness components (Ca and Mg ions) contained in raw waters such as industrial and domestic waters have been used for example for pretreatment of water for refrigeration apparatuses such as condensers and boilers and pure water-producing apparatuses for prevention of fouling in the apparatus.
For example, hardness components in raw water are replaced with Na ions in a water-softening apparatus containing ion-exchange resin that is connected to the water-supply line and the softened water obtained is used as feed water.
Because there may be leakage of the hardness components (so-called hardness leakage) for example due to ineffective regeneration or degradation of the ion-exchange resin described above, the leakage of the hardness components is monitored. For example, Patent Document 1 discloses a technology of detecting hardness leakage by using a “hardness indicator comprising Eriochrome Black T (EBT), a pH buffering agent, and a masking agent as main components and additionally Mg-EDTA added thereto”.
Recently for reliable or efficient operation of the apparatuses described above, automatic analyzers that analyze the hardness components contained in sample water have been used and the leakage of the hardness components is monitored continuously or periodically (see, e.g., Patent Document 2).